E6-13453. Airworthiness Directives; Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for certain Learjet Model 23, 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D, 25F, 28, 29, 31, 31A, 35, 35A (C-21A), 36, 36A, 55, 55B, and 55C airplanes. This proposed AD would require modifying the left- and right-hand standby fuel pump switches. This proposed AD would also require revising the Emergency and Abnormal Procedures sections of the airplane flight manual to advise the flightcrew of the proper procedures to follow in the event of failure of the standby fuel pump to shut off. This proposed AD results from a report of inadvertent operation of a standby fuel pump due to an electrical system malfunction. We are proposing this AD to prevent this inadvertent operation, which could result in inadvertent fuel transfer by the left or right wing fuel system and subsequent over-limit fuel imbalance between the left and right wing fuel loads. This imbalance could affect lateral control of the airplane which could result in reduced controllability.

DATES:

We must receive comments on this proposed AD by October 2, 2006.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility, U.S. Department of Transportation, 400 Seventh Street SW., Nassif Building, room PL-401, Washington, DC 20590.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

Contact Learjet, Inc., One Learjet Way, Wichita, Kansas 67209-2942, for the service information identified in this proposed AD

FOR FURTHER INFORMATION CONTACT:

James Galstad, Aerospace Engineer, Systems and Propulsion Branch, ACE-116W, FAA, Wichita Aircraft Certification Office, 1801 Airport Road, Room 100, Mid-Continent Airport, Wichita, Kansas 67209; telephone [phone]; fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to submit any relevant written data, views, or arguments regarding this proposed AD. Send your comments to an address listed in the ADDRESSES section. Include the docket number “FAA-2006-25563; Directorate Identifier 2006-NM-083-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov.

Examining the Docket

You may examine the AD docket on the Internet at http://dms.dot.gov,, or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone [phone]) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them.

Discussion

We have received a report indicating that inadvertent operation of a standby fuel pump due to an electrical system malfunction occurred on a Learjet Model 35A (C-21A) airplane. This condition, if not corrected, could result in inadvertent fuel transfer by the left or right wing fuel system and subsequent over-limit fuel imbalance between the left and right wing fuel loads. This imbalance could affect lateral control of the airplane which could result in reduced controllability.

Relevant Service Information

We reviewed the Bombardier service bulletins identified in the following table:

Service Information

Service bulletin	Revision level	Date	Learjet model(s)
23-28-6	Original Issue	April 21, 1998	23
24/25-28-3	2	February 21, 1998	24/25
28/29-28-4	3	June 2, 1999	28/29
31-28-7	3	January 26, 2001	31
35/36-28-11	4	December 4, 2000	35/36
55-28-13	3	December 15, 2000	55

The service bulletins describe the following procedures: For airplanes on which the replacement of the standby fuel pump switch has been accomplished per the original or earlier revisions of the applicable referenced service bulletins, the procedures include installing fuses and fuse holders, and modifying the electrical wiring. For airplanes on which the replacement has not been accomplished per the original issue or earlier revisions of the applicable referenced service bulletins, the procedures include replacing the standby fuel pump switches, installing the fuel pump dimming box assembly, and modifying the electrical wiring. The procedures also describe verifying that the subject temporary flight manual (TFM) changes have been incorporated into the applicable airplane flight manual (AFM).

We have also reviewed the following Learjet TFM changes:

TFM	Date
TFM 96-08	May 30, 1996.
TFM 96-09	May 30, 1996.
TFM 98-01	May 11, 1999.
TFM 98-02	May 11, 1999.

The TFMs describe procedures for revising the Emergency and Abnormal Procedures sections of the AFM to advise the flightcrew of the proper procedures to follow in the event of failure of the standby fuel pump to shut off. Accomplishing the actions specified in the service information is intended to adequately address the unsafe condition.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other airplanes of this same type design. For this reason, we are proposing this AD, which would require accomplishing the actions specified in the service information described previously.

Costs of Compliance

There are about 1,613 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this proposed AD, at an average labor rate of $80 per work hour, depending on airplane configuration.

Estimated Costs

Action	Work hours	Parts	Cost per airplane	Number of U.S.-registered airplanes	Fleet cost
Modification	Between 4 and 12	Between $1,426 and $1,470	Between $1,746 and $2,430	1,150	Between $2,007,900 and $2,794,500.
AFM Revision	1	None	$80	1,150	$92,000.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government.

For the reasons discussed above, I certify that the proposed regulation:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and

3. Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. The Federal Aviation Administration (FAA) amends § 39.13 by adding the following new airworthiness directive (AD):

Learjet: Docket No. FAA-2006-25563; Directorate Identifier 2006-NM-083-AD.

Comments Due Date

(a) The FAA must receive comments on this AD action by October 2, 2006.

Affected ADs

(b) None.

Applicability

(c) This AD applies to the Learjet models identified in the applicable Bombardier service bulletin listed in Table 1 of this AD.

Table 1.—Applicability by Service Bulletin

Service bulletin	Revision level	Date	Learjet model(s)
23-28-6	Original Issue	April 21, 1998	23.
24/25-28-3	2	February 21, 1998	24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, and 24F-A; 25, 25A, 25B, 25C, 25D, and 25F.
28/29-28-4	3	June 2, 1999	28 and 29.
31-28-7	3	January 26, 2001	31 and 31A.
35/36-28-11	4	December 4, 2000	35 and 35A (C-21A); 36 and 36A.
55-28-13	3	December 15, 2000	55, 55B and 55C.

Unsafe Condition

(d) This AD results from a report of inadvertent operation of a standby fuel pump due to an electrical system malfunction. We are issuing this AD to prevent this inadvertent operation, which could result in inadvertent fuel transfer by the left or right wing fuel system and subsequent over-limit fuel imbalance between the left and right wing fuel loads. This imbalance could affect lateral control of the airplane which could result in reduced controllability.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.

Modification

(f) Within 24 months after the effective date of this AD: Modify the left- and right-hand standby fuel pump switches, in accordance with the Accomplishment Instructions of the applicable service bulletin identified in Table 1 of this AD.

Airplane Flight Manual (AFM) Revision

(g) Before further flight after accomplishing the modification required by paragraph (f) of this AD: Revise the Emergency and Abnormal Procedures sections of the applicable AFM to advise the flightcrew of proper procedures to follow in the event of failure of the standby fuel pump to shut off by including the information in the Learjet temporary flight manual (TFM) Changes identified in Table 2 of this AD.

Table 2.—TFM Changes

Learjet model(s)	TFM	Date
24/25, 28/29, 31, 35/35, 55	TFM 96-08	May 30, 1996.
24/25, 28/29, 31, 35/35, 55	TFM 96-09	May 30, 1996.
23	TFM 98-01	May 11, 1999.
23	TFM 98-02	May 11, 1999.

This may be done by inserting a copy of the TFM changes into the AFM. When the TFM changes have been included in the general revisions of the AFM, those general revisions may be inserted into the AFM, provided the relevant information in the general revisions is identical to that in the TFM changes.

Alternative Methods of Compliance (AMOCs)

(h)(1) The Manager, Wichita Aircraft Certification Office (ACO), FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.

(2) Before using any AMOC approved in accordance with § 39.19 on any airplane to which the AMOC applies, notify the appropriate principal inspector in the FAA Flight Standards Certificate Holding District Office.

Issued in Renton, Washington, on August 3, 2006.

Ali Bahrami,

Manager, Transport Airplane Directorate, Aircraft Certification Service.